Delayed electron capture and Mu- formation in ZnSe

We have investigated a single crystal of the wide bandgap II-VI semiconductor ZnSe. The sample was highly resistive due to heavy compensation of this n-type semiconductor. In low transverse fields, clear signs of conversion from a paramagnetic to a diamagnetic fraction are observed, at about 60 K. The data are interpreted as delayed electron capture by paramagnetic muonium, forming the negatively charged state Mu-. The implications with respect to the electrical activity of muonium, and by analogy hydrogen, in this semiconductor are analyzed.